A number of electric lamp types, particularly tungsten-halogen, metal halide and high-pressure mercury, employ a feedthrough comprised of a molybdenum foil which is sealed into a fused quartz, fused silica, or other high-silica-content glass envelope in order to provide an electrical connection between the inner and outer electric leads. The molybdenum foil has a better thermal expansion match to the high-temperature, low-expansion glass than the electric leads which are usually tungsten. The foil is sealed within the glass by pressing or pinching the hot, softened glass to encase the foil and form a hermetic seal. This technique is well-known in the art, various examples of which may be found in U.S. Pat. Nos. 5,021,711, 5,142,195 and 4,540,373, which are incorporated herein by reference.
One particular condition that adversely effects the seal is oxidation of the molybdenum foil during operation of the lamp. The oxidation causes a degradation of the electrical conductivity of the foil, which reduces the performance of the lamp and, ultimately, causes a failure of the lamp. If the oxidation becomes extreme it can cause failure of the seal itself, which also leads to the lamp failure.